Improved Real-Power Loss Minimisation

The problem of the reactive control of a power system is formulated as a static optimisation technique to ensure the minimisation of the real-power system losses by controlling the switchable reactive power sources, generator terminal voltages, transformer tap ratios and phase shiftet's. The objective function as well as the constraints  are established using the linearized sensitivity relationships of power system state and control variables and standard linear programming routines are used to determine the optimum operating condition; the fast-decoupled load flow technique is employed because it is fast, simple and has less computer storage. Results of the application of this development to the IEEE 14 bus system is presented

Assessment of Long-Run Marginal Costing of Transmission and Distribution Expansion

The Long-Run Marginal Costing (LRMC) technique is used as a cost-reflecting pricing method and finds useful application in the recovery of the total investment cost for the use of a transmission or distribution network. This paper reviews recent applications of this technique based on some examples from United Kingdom, Greece and Oman. Then using typical practical networks as case studies, this paper compares two different methods for the determination of the LRMC of transmission and distribution expansion/reinforcement: the average incremental cost (AIC) methodology and marginal incremental costs (MIC) techniques. Based on the results obtained, it is concluded that the AIC technique is easier to implement and explain because of its price stability

Technical Note: On the Correctness of Load Loss Factor

Load Loss Factor (LLF) is a function of the estimate of the losses between the grid supply point and the consumers. It varies with voltage levels and types of consumers (such as domestic, industrial or commercial). This technical note compares the accuracy of LLF derived from exact daily and seasonal variation in demand and estimated values from the system load factor (LF).http://dx.doi.org/10.4314/njt.v34i3.1

Stochastic Fault Analysis of Balanced Systems

A sequence coordinates approach for fault calculations is extended to take into account the uncertainty of the network input data. The probability of a fault current on a bus exceeding its short circuit current is determined. These results would be of importance in determining the protective philosophy of any network. The simple 6-bus Saskatchewan Power Corporation System is used to demonstrate the features of this new development

Investigations into the transformer inrush current problem

A transformer being energised may draw a large transient current from the grid supply, resulting in a temporary voltage dip at the point of connection (POC) where customers are connected. The voltage dip is dependent upon the magnitude of the transformer inrush current. The peak current of the first cycle, under worst conditions, is considered important. This paper presents the results achieved following the energisation of a 10MVA 132/11kV transformer as well as the practical mitigation measures to minimise the impact of the transformer energisation.Keywords: transformer saturation; transformer inrush current modelling; voltage drop; PSCAD softwar

The Impact of Distributed Generation on Distribution Networks

Distributed Generators (DG or embedded generators) are generators that are connected to the distribution network. Their advantages are the ability to reduce or postpone the need for investment in the transmission and distribution infrastructure when optimally located; the ability to reduce technical losses within the transmission and distribution networks as well as general improvement in power quality and system reliability. This paper highlights the benefits of distributed generation by using a 15-bus radial distribution network, modelled in the DIgSILENT Power Factory software, to demonstrate the improvement in voltage profile as well as the reduction in technical losses.http://dx.doi.org/10.4314/njt.v34i2.1

Voltage stability analysis of the Nigerian Power System using annealing optimization technique

The paper addresses the means of overcoming the challenge posed by voltage collapse to the stability of the Nigerian electric power system. The technique applied is based on time identification algorithm elaborating, at a given grid bus, the local phasor measurements at fast sampling rate. Elements such as adjustable shunt compensation devices, generator reactive generation, transformer tap settings are optimally adjusted at each operating point to reach the objective of minimizing the voltage stability index at each individual bus as well as minimizing the global voltage stability indicator. The control elements setting were optimized and the maximum possible MVA voltage stable loading has been achieved and a best voltage profile was obtained. Results of tests conducted on a 6-bus IEEE system and a typical 28-bus Nigerian power distribution network are presented and discussed. Keywords: Special protection systems, voltage stability analysis, voltage stability limit, voltage collapse mechanism, system securit

Improvement of bus voltage profiles of Nigerian power network in the presence of Static Synchronous Compensator (STATCOM) and Doubly Fed Induction Generator (DFIG)

Frequent blackouts and unstable supply of electricity show that the  voltage instability problem has been one of the major challenges facing the power system network in Nigeria. This study investigates the voltage stability analysis of the Nigerian power network in the presence of renewable energy sources; FACTS device is used as a voltage controller. A 330kV, 28-bus power system network was studied using the PSS/E software-based Newton-Raphson load-flow technique. The results show that 10 out of the 28 buses had voltages lying below the statutory limit of 0.95 ≤ 1.05 p.u. The application of STATCOM and DFIG devices on two of the weakest buses restored the voltages to acceptable statutory limits. The total active and reactive power losses were reduced to 18.76% and 18.82% respectively. Keywords: Voltage stability analysis; Integration of renewable energy sources; FACTS controllers, Reactive Power, Power Flow

OPTIMAL LOCATION OF DISTRIBUTED GENERATION ON THE NIGERIAN POWER SYSTEM

The optimal sizing and location of distributed generators (DG) remain crucial factors in their application for active power loss minimization as well as voltage profile improvement. This paper describes an analytical method for the optimal sizing and placement of DG in the Nigerian power network for active power loss minimization. The effectiveness of the proposed method showed a 6.2% reduction in active power losses on the 33kV Nigerian network (i.e. from 92.7MW to 87.0MW). The results showed an improvement in the voltage profile of that six load buses whose voltages were outside the statutory limit of 0.95 pu≤ Vi ≤ 1.05pu.